Acoustic Panel Resonators for Low-Frequency Absorption
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Solution Overview
Problem
Conventional acoustic panels using porous materials struggle to effectively absorb low-frequency sounds, particularly those below 1000 Hz, due to limitations in sound absorption coefficients and increased size and weight when attempting to improve low-frequency attenuation.
Innovation Solution
An acoustically absorbent cell design featuring a porous matrix with strategically arranged resonators, where at least two resonators are positioned perpendicular to each other's faces, and each resonator has unique dimensional parameters to optimize absorption across a wide frequency range, enhancing the absorption coefficient by resonance and diffusion mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness and mass of porous matrix are increased to improve low-frequency sound absorption, then the sound attenuation performance at low frequencies is improved, but the size and weight of the acoustic panel increase significantly
Solution Approach 1:
The patent changes the physical parameters of the porous matrix by introducing resonators with specific dimensional characteristics (cavity volume, neck dimensions) that create resonance at low frequencies. This allows thin panels (5-10 cm) to achieve low-frequency absorption without increasing thickness or mass, as the resonators exploit acoustic resonance phenomena rather than relying on material mass.
Solution Approach 2:
The patent creates a composite structure combining porous matrix material with embedded resonators (such as Helmholtz resonators or cavity resonators). This composite design leverages both the broadband absorption of porous materials and the targeted low-frequency resonance enhancement, achieving superior low-frequency performance in a thin, lightweight configuration.
2Reliability
If resonators are embedded in porous matrix to enhance low-frequency absorption, then the absorption coefficient at low frequencies is significantly increased, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The patent utilizes the inherent porous structure of the matrix material as the primary absorption mechanism, which is simpler to manufacture than fully dense resonator structures. The porosity provides natural broadband absorption while allowing embedded resonators to be integrated more easily into the matrix structure.
Solution Approach 2:
The resonators are designed to serve multiple functions: they provide low-frequency resonance absorption, act as structural reinforcement elements within the porous matrix, and can be manufactured using standard industrial techniques. This multi-functionality reduces overall structural complexity despite the added resonance capability.
3Reliability
If multiple resonators with different dimensional parameters are arranged perpendicular to each other's faces, then the absorption coefficient across a wide frequency range is optimized, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies different resonator configurations to different local regions of the panel. By arranging resonators with varying dimensional parameters in specific orientations (perpendicular to each other's faces), the design creates localized absorption optimization that collectively achieves broad frequency coverage without requiring ultra-precise positioning of every individual resonator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves significant absorption of low-frequency sounds with an absorption coefficient greater than 0.8 across a wide frequency range, maintaining high performance up to 6000 Hz while maintaining a reduced panel thickness, suitable for integration into acoustic panels without significant size or weight penalties.
Implementation Method 1
Some of the acoustic energy is also absorbed due to the resonance of the resonators at their resonant frequency
Implementation Method 2
These structures attenuate acoustic energy through viscous and thermal losses
Implementation Method 3
The resonators integrated into the porous matrix act as diffusers, reflecting the incident acoustic wave in all directions
Data Source
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Figure 7~10B
AI summary
The invention concerns an acoustically absorbent cell (22, 48) for an acoustic panel, comprising a layer (32) having a porous matrix incorporating a plurality of acoustic resonators (A1-A4, Bi-B6) between a first face (30, 54) and a second face (28, 56) of the porous matrix (32). According to the invention, the resonators (A1-A4, Bi-B6) are, for example, ordered in such a way as to form at least two substantially parallel rows (24, 26, 50, 52) each comprising at least two resonators and extending along the first and second faces.